The known mechanisms preventing rate variations caused by gravity on a balance-spring regulating device as described for example in patent EP 2 124 111 of the patentee, but also as described for example in documents EP-A-2031465 or EP-A-1615085, are disadvantageous in that the balance-spring is subjected to high accelerations caused by the movements of the mobile platform bearing this balance-spring during sudden movements of the wearer of the watch. These accelerations can cause a knocking phenomenon in the balance which causes a rate variation in this regulating device, generally a gain therein.